Self supporting pleatable web and an oil filter including the same

ABSTRACT

A fibrous media suitable for an oil filter comprising a fibrous web formed from synthetic fibers; optionally at least one additive, and a thermoset binder present at a concentration of at least 15 wt.-% by weight of the fibrous web and/or at least one binder fiber, wherein the synthetic fibers comprise up to 30 wt.-%, preferably up to 20 wt.-%, glass fibers, based on the total weight of the fibers. The fibers are bonded with the thermoset binder and/or the at least one binder fiber to form a web; and the fibrous media is capable of forming a self-supporting, pleated oil filter media which is capable of retaining pleats upon contact with oil having a temperature in the range encountered in a combustion engine.

TECHNICAL FIELD

The present invention relates to filter media for oil filters. Inparticular, the present invention relates to filter media formed fromsynthetic fibers, optionally at least one additive and at least onethermoset binder and/or at least one binder fiber, wherein the syntheticfibers comprise up to 30 wt.-%, preferably up to 20 wt.-%, glass fibers,based on the total weight of the fibers, wherein the fibers are bondedwith the thermoset binder and/or the at least one binder fiber to form afibrous medium. The invention also relates to a method of producing suchfilter media as well as to self-supporting pleated oil filters producedfrom the media.

BACKGROUND

Oil filters intended for use in combustion engines conventionallycomprise filter media with fibers obtained from wood pulp. Such woodpulp fibers are typically 1 to 7 millimeters long and 15 to 45 micronsin diameter. Natural wood pulp has largely been the preferred rawmaterial for producing filtration media due to its relatively low cost,processability, various mechanical and chemical properties, anddurability in the end application.

The filter media are pleated to increase filtration surface areatransversally to the direction of the oil flow.

U.S. Pat. No. 3,288,299 discloses a dual type of oil filter cartridgewherein part of the flow is through a surface type of filter element,such as pleated paper, and the rest of the flow is through a depth typeof filter element such as a thick fibrous mass. An oil filter andadapter is disclosed in U.S. Pat. No. 3,912,631.

A typical prior art oil filter is shown in FIG. 1. Reference numeral 1refers to the pleated filter media (or filtration media) and 2 to abacking structure. A conventional filter media exhibits low stiffnessand has poor mechanical strength in terms of tensile strength and burststrength. The filter media 1 is therefore used together with a metalmesh or other type of pleat shape when used in the end application.

Nevertheless, in view of the low mechanical strength the filter mediatend to burst over time on exposure to engine oil at the temperaturesencountered in a combustion engine, such as 125-135° C.

Although filter media products that are produced largely with wood pulpare still an excellent choice for most automotive and heavy duty oilfiltration applications, there is a growing market demand for oilfiltration products that exhibit increased strength and durability overtime as the media is exposed to the various chemical, thermal, andmechanical stresses of the end application environment. This demandstems from both harsher end application conditions that the media isexposed to as well as increasing demand for filter media that can besafely used in the end application for increasingly longer amounts oftime without rupturing or failing.

The long-standing and widely applied solution to this demand has been toincorporate some minor quantity of synthetic fiber, typically PETpolyester, in the amount of about 5-20%. The result of fortifying thefiber furnish in this way is higher media strength as well as enhancedchemical and mechanical durability when the media is exposed to the endapplication environment, due to the superior chemical, thermal, andmechanical durability of the synthetic fibers themselves.

For air filters there are alternative technical solutions primarilybased on non-natural fibers described in the art.

U.S. Pat. No. 7,608,125 discloses a MERV filter composed of a wet laidfibrous mat comprising about 20-60 wt-% of glass fibers, about 15-60wt-% of polymer fibers, and about 15-40 wt-% of a binder for bonding ofthe fibers. The binder of this disclosure is latex modified withmelamine formaldehyde.

Published US Patent Application No. 2012/0175298 discloses a HEPA filtercomprising a nonwoven web of two different fiber components. The firstfiber component is formed by fibers of polyesters, polyamides,polyolefin, polylactide, cellulose esters, polycaprolactone, up at least20% of the weight of web. The second fiber can be composed of eithercellulosic fibres (Lyocell) or glass or combination of the two. There isfurther a binder component formed by acrylic polymers, styrenicpolymers, vinyl polymers polyurethanes, and combinations thereof.

Published US Patent Application No. 2013/0233789 discloses a glass-freenon-woven fuel filtration media that is comprised of a blend of a staplesynthetic fibers and fibrillated cellulosic fibers.

U.S. Pat. Nos. 7,488,365, 8,236,082 and 8,778,047 disclose furtherfiltration media containing 50 to 100% of synthetic fibers of the weightof the fibrous web.

None of the references to air filters and fuel filter media discloses afilter medium capable of forming a self-supporting oil filter whenconfigured into a pleated structure and which would be capable ofworking properly at the harsh conditions in connection with a combustionengine.

In fact, the known filtration media containing a high percentage ofsynthetic fibers are not pleateable or self-supporting as such, and theyhave to be co-pleated and reinforced with some sort of additionalmechanical support layer, such as a plastic or wire mesh backing. Mediamade with high levels of synthetic fiber typically tend to exhibit drapeand they lack sufficient stiffness and rigidity causing the pleats tocollapse without an additional support. A 100% synthetic media asdisclosed in the art cannot maintain a grooving pattern like corrugationor a pleated structure due to the thermal and mechanical properties ofthe synthetic fibers.

SUMMARY

The following presents a simplified summary in order to provide a basicunderstanding of some aspects of various embodiments of the invention.

The summary is not an extensive overview of the invention. It is neitherintended to identify key or critical elements of the invention nor todelineate the scope of the invention. The prelude to a more detaileddescription of exemplifying embodiments of the invention.

It is an aim of the present invention to eliminate at least some of theproblems related to the art and to provide a novel kind of filter mediawhich is capable of use as an oil filter in combustion engines.

According to one aspect the present disclosure concerns aself-supporting pleatable fibrous web for an oil filter, which webcomprises synthetic fibers, optionally at least one additive, at leastone binder fiber and/or a thermoset binder present at a sufficientlyhigh concentration, such as e.g. at least 15% by weight of the fibrousweb, to allow for bonding of the fibers to form a web and for renderingthe fibrous media capable of forming a self-supporting, pleated oilfilter, wherein the synthetic fibers comprise up to 30 wt.-%, preferablyup to 20 wt.-%, glass fibers, based on the total weight of the fibers.The media thus obtained is capable of retaining pleats upon contact withoil having a temperature in the range typically encountered in acombustion engine, such as 125-135° C. (257-275° F.).

A filtration media (or filter media) of the present kind can, in anaspect of the present disclosure, be produced by forming a wet laid webfrom a fibrous slurry comprised of synthetic fibers and optionally atleast one binder fiber and/or at least one additive; drying the web to alow moisture content; contacting the dried web with a composition of athermoset binding agent in a liquid phase to bond the fibers togetherwith the thermoset binder; removing the liquid phase to form a media,optionally corrugating and/or pre-curing the obtained media and pleatingthe obtained media, followed by an optional final curing step.

Another aspect relates to oil filters for combustion engines whichincorporate filter media of the indicated kind.

A still further aspect of the present disclosure relates to the use ofthermoset resins for preventing damage of an oil filter caused by acombination of oil and antifreeze agents and decomposition productsthereof.

More specifically, the present filter media is characterized by what isstated in the characterizing part of claim 1.

characterizing part of claim 23.

The present oil filter is characterized by what is stated in thecharacterizing part of claim 32, and the present use is characterized bywhat is stated in claim 34.

Considerable advantages are obtained by the present invention: Thepresent fibrous media will give rise to self-supporting (i.e.stand-alone or unsupported) filters when pleated, optionally corrugatedand shaped into the proper form of an oil filter, and do not require theuse of a mesh backing in the finished filter device. Therefore they canbe manufactured and supplied without the need of pairing with a mesh orother type of secondary material backing.

The present fibrous media are suitable as oil filters and exhibit goodburst strength over time on exposure to hot engine oil.

The present fibrous media have lower degradation rates when exposed tohot engine oil than conventional filtration media that contain naturalwood pulps.

As will be discussed below in more detail, synthetic materials forexample comprising prior art fiber mixtures of the kind discussed above,would be vulnerable to glycol assisted disintegration which prevails atthe conditions in, for example heavy duty diesel engines. Upondecomposition, such materials may disintegrate into the oil and evengive rise to engine seizure and contamination of moving parts. Bycontrast, the present fibrous media have improved resistance to suchdisintegration and this provides extended operation times for thefilters.

The fibrous media according to the present invention is readilygroovable, i.e. corrugatable, and pleatable. And the material is capableof maintaining most of its original groove depth (or corrugation depth)even after long exposure times in hot engine oil having e.g. atemperature of 140° C. This feature also contributes to extendedoperation life of the present fibrous media.

produced on typical style production equipment without undueinefficiencies such as those that may arise from web breaks, linting,wrinkling, etc.

In summary, the present invention eliminates the use of expensivebacking materials, the obtained fibrous media are easily groovable (orcorrugatable) and are easily pleatable. The end result is the ability toproduce a filter with the present fibrous media without a supportbacking material while also achieving significantly higher burststrength than possible with traditional style oil filtration media thatcontain wood pulps, excellent resistance to glycol assisteddisintegration and excellent dust filtration capacity and particleremoval efficiency.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows an oil filter system according to prior art which includestwo supporting structures for maintaining the pleats during use in e.g.a combustion engine;

FIG. 2 shows the natural logarithm (ln) of the hot oil burst strength ofa non-limiting exemplary fibrous medium of the present invention (♦) andtypical wood pulp containing media (▪, x, X), as a function of time,thereby demonstrating the beneficial hot oil durability of the fibrousmedia according to the invention (the conditions for this hot oil ageingare described in the test methods below);

FIG. 3 shows an exemplary non-limiting pleated self-supporting mediumaccording to the present invention;

FIG. 4 shows a non-corrugated pleated filter medium (left) and acorrugated pleated filter medium (right), thereby illustrating theimproved flow through the pleats when using a corrugated pleated filtermedium; and

FIG. 5 shows the relation between caliper, total thickness andcorrugation depth of a non-limiting exemplary fibrous medium of thepresent invention.

EMBODIMENTS

A number of exemplifying and non-limiting embodiments of the inventionare described in the accompanied dependent claims.

neither exclude nor require the existence of also un-recited features.The features recited in depending claims are mutually freely combinableunless otherwise explicitly stated. Furthermore, it is to be understoodthat the use of “a” or “an”, i.e. a singular form, throughout thisdocument does not exclude a plurality.

The term “consisting essentially of” has the meaning that specificfurther components may be present, namely those not materially affectingthe essential characteristics of the fibers/composition in question.

As discussed above, in a preferred embodiment, the present fibrous mediasuitable for an oil filter comprises a fibrous web formed from syntheticfibers, optionally at least one additive, at least one binder fiberand/or a thermoset binder which is preferably present at a concentrationof at least 15 wt-% by weight of the fibrous web, wherein the syntheticfibers comprise up to 30 wt.-%, preferably up to 20 wt.-%, glass fibers,based on the total weight of the fibers. The fibers are bonded with thethermoset binder and/or the binder fiber to form a fibrous media. Thefibrous media thus obtained is capable of forming a self-supporting,pleated oil filter which is capable of retaining pleats and corrugationsupon contact with oil having a temperature in the range encountered in acombustion engine such as e.g. 125 to 135° C.

Generally, the concentration of the thermoset binder is preferably inthe range of 15 to 50 wt-% by weight of the fibrous web, in particular15 to 30% by weight of the fibrous web. At a concentration of 15 wt-% orgreater, excellent properties in terms of pleatability andself-supportability are achieved. At concentrations up to about 30%,efficiency of the filter as a filtering media is still unimpaired,although greater concentrations can still be used.

“Synthetic” is herein used to differentiate the present fibers fromnatural fibers obtainable directly from natural raw-materials. Thus, forthe purpose of the invention, “synthetic” fibers include fibers ofpolymeric materials produced by polymerization of monomeric entities aswell as fibers obtained by drawing of melt material and fibers obtainedby regenerating natural fibers e.g. after dissolution of them in asolvent.

thermoplastic polymers, silicious fibers, such as glass fibers,regenerated cellulosic fibers and mixtures thereof.

In one embodiment, synthetic fibers of only one kind are used in thefibrous web.

In another embodiment, it is particularly preferred to use at least twodifferent synthetic fibers.

In a further embodiment, at least 30 wt.-%, preferably at least 50 wt.-%of the fibers are thermoplastic polymers, based on the total weight offibers.

Thus, in one particular embodiment, the fibrous media comprises

-   -   a first fiber component consisting of fibers selected from the        group of synthetic thermoplastic fibers;    -   a second fiber component consisting of fibers selected from a        group of silicious fibers and optionally further comprising        regenerated cellulosic fibers, and combinations thereof;    -   optionally a third fiber component consisting of binder fibers;    -   the fibers of the first and the second and optionally the third        fiber components being mixed together, and    -   a thermoset binder wherein the thermoset binder is being capable        of bonding together the first, the second and optionally the        third fiber components.

According to another aspect the present disclosure concerns an oilfilter which essentially consists of a self-supporting fibrous web whichcomprises:

-   -   a first fiber component consisting of fibers selected from the        group of synthetic thermoplastic fibers;    -   a second fiber component consisting of silicious fibers; the        fibers of the first fiber component forming a majority of the        fibers of the fibrous web; and    -   a thermoset binder which forms at least 15%, by weight of the        fibrous web.        embodiments, the first fiber is preferably a synthetic        thermoplastic fiber, such as polyester, and forming 30 to 99.5%,        in particular 40 to 99%, for example 43 to 98% by weight of the        fibers of the fibrous web.

The second fiber is selected from a group of glass fibers, optionallymixed with Lyocell, regenerated cellulose and combinations thereof. Theamount of the second fiber is preferably 0.1 to 70%, in particular 1 to60%, for example 2 to 57% by weight of the fibers of the fibrous web.

As defined herein, the term “self-supporting pleatable web” orself-supporting pleated filter media” is a web or a filter media whosepleats have sufficient stiffness so that they do not collapse or bowexcessively when subjected to oil pressure typically encountered incombustion engines. In one preferred embodiment, the media can beprovided with pleats having a sharp angle of less than 30°, inparticular less than 25° (see also FIG. 3). Typically, a “pleatable”media will be capable of taking up pleats and retaining them.Preferably, the pleated media will retain pleats over the wholeoperation time of the filter.

As defined herein, the term “corrugation” or “grooving” has the meaningcommonly used in the art. Specifically, it can be preferably defined asrelating to a surface structure of alternate ridges or grooves and istypically applied in a direction perpendicular to the pleat direction inorder to further increase the effective surface area of the mediawithout the necessity of increasing the outer dimensions of the media.Preferably, the corrugation depth (or grooving depth) is about 0.1-0.6mm. The “corrugation depth” relates to the difference between thecaliper (or thickness) of the flat sheet of medium and the thickness ofthe sheet after corrugating the medium (see also FIG. 5). Corrugation isparticularly important in coiled filter arrangements of pleated filtersin which the pleats extend parallel to the central axis of the coiledfilter arrangement. As the number of pleats increases within a givenvolume, the pleats come to lie in close abutment against one another, inparticular on the outflow side of the filter, thereby reducing theflowrate of the medium to be filtered and consequently increasing flowresistance of the filter arrangement (see also FIG. 4, right sideshowing a corrugated filter system according to the invention). Thus,corrugation allows for an compared to a non-corrugated filter as e.g.shown in FIG. 4, left side.

As defined herein, the term “fibrous” means a material that is composedpredominantly of fiber and/or staple fiber.

In the present context, the term “thermoplastic” means a plastic whichbecomes pliable or moldable above a specific temperature and returns toa solid state upon cooling. Exemplary thermoplastic fibers suitable forthe present disclosure are polyesters (e.g., polyalkylene terephthalatessuch as polyethylene terephthalate (PET), polybutylene terephthalate(PBT) and the like), polyalkylenes (e.g., polyethylenes, polypropylenesand the like), poyacrylonitriles (PAN), and polyamides (nylons, forexample, nylon-6, nylon 6,6, nylon-6,12, and the like).

Preferred are PET fibers which exhibit good chemical and thermalresistance which are properties of importance for the use of the mediaas oil filters.

In an embodiment, the thermoplastic synthetic fibers are selected fromfibers having an average diameter from 0.1 um to 15 um, such as 0.1 umto 10 um, and an average length from 1 to 50 mm, such as 1 to 20 mm. Ingeneral, fibers having a length greater than 5 mm, in particular greaterthan 10 mm, are preferred for good burst strength.

In the present context, “silicious fibers” primarily stands for “glass”fibers such as microglass fibers. Such fibers generally have an aspectratio (ratio of length to diameter) of 1,000 to 1.

In one embodiment, the glass fibers have an average diameter from 0.1 umto 5 um, and an aspect ratio of 1,000 to 1. In particular, the glassfibers may have an average fiber diameter of 0.4 to 2.6 um.

Glass fibers are preferably included in a sufficient amount to improveefficiency of the fibrous media as a filter. In one embodiment, thesynthetic fibers comprise up to 30 wt.-%, preferably up to 20 wt.-%,based on the total weight of the fibers, of glass fibers. Although thesynthetic fibers comprise only up to 30 wt.-% or up to 20 wt.-% of glassfibers, based on the total weight of the fibers, this amount issufficient to prepare a fibrous media for a filter examples. Typically,synthetic filter media of the prior art include a high amount of glassfibers for achieving a sufficient filtration efficiency of a gas or aliquid, even under high temperature conditions such as e.g. 150° C.However, by using less glass fibers in the fibrous media as set forth inthe claims, fibrous media may be provided that have excellent filtrationproperties in terms of particle removal efficiency and hot oil burststrength.

In particularly preferred embodiments, there are at least two kinds ofglass fibers present, viz. a first group of fibers having an averagefiber diameter of less than 1 um and a second group which having anaverage fiber diameter of 2 um or more. The weight ratio of the twogroups of fibers is typically 1:100 to 100:1, in particular about 1:10to 10:1.

The synthetic fibers may also include up to 40% by weight, preferably upto 30% by weight, based on the total weight of the fibers, of aregenerated cellulosic material, such as Lyocell or viscose orcombinations thereof.

In a further embodiment, the present fibrous media suitable for an oilfilter comprises a fibrous web formed from, or comprising,

-   -   a first fibrous component consisting of synthetic thermoplastic        fibers, the synthetic fibers having an average diameter from 0.1        um to 10 um and an average length from 1 to 20 mm; and    -   a second fibrous component consisting of silicious fibers; the        fibers of the first fibrous component forming a majority of the        fibers of the fibrous web such as up to 70% by weight, based on        the total weight of the fibrous components; and    -   a thermoset binder present at a concentration of at least 15%,        by weight of the fibrous web.

According to another embodiment the fibrous web according to the presentdisclosure comprises a combination of first and second fibrouscomponents, wherein

-   -   the first fibrous component forms 70% to 88% of the fibrous web        by weight;    -   the second fibrous components, of for example glass fibers,        forms 12% to 30% of the fibrous web by weight.        such as undrawn thermoplastic synthetic fibers. Undrawn fibers        are common in the art. Although undrawn fibers typically do not        have the mechanical properties such as tensile strength and        modulus that are required for practical use, it was surprisingly        found out that undrawn fibers may improve the web's capability        for retaining not only pleats but also corrugation upon contact        with oil having a temperature in the range encountered in a        combustion engine such as 125 to 135° C. They may also        contribute to improve the filter efficiency of the filter as        defined herein.

Undrawn fibers may be comprised up to 50% by weight, preferably up to45% by weight, such as from 20 to 50% by weight or from 20 to 40% byweight, based on the total weight of the fibers.

Preferred are undrawn PET fibers. The undrawn fibers may preferably havean average fiber length of about 1 to 10 mm, such as about 5 to 10 mm.

By using undrawn synthetic fibers and by e.g. calendering the resultingwet-laid fibrous web under heat (e.g. up to 220° C.) and pressure usingboth top and bottom hot smooth rolls, the void fraction of the obtainedfibrous web may be preferably adjusted in the range of approximately70-95%, such as 80-90% which may be particularly beneficial forcorrugation. This is because if, on the one hand, the void fraction istoo low, the corrugation is easily embossed, but the filter propertiesof the resulting corrugated fibrous web are not sufficient. If, on theother hand, the void fraction is too high, then the fibrous web cannotbe corrugated in the most preferred corrugation depth such as 0.1-0.6mm. Moreover, the calendering may add strength for the furtherprocessing steps such as the corrugation, impregnation with thethermoset binder and/or pleating.

Without being bound by this theory, it is believed that the undrawnfibers may basically act as additional binder fibers, since theycontract after being heated under the manufacturing conditions asdescribed below in example 1.

The present media further includes a binder, in particular a thermosetbinder, which preferably has a concentration of 15% to 50% by weight ofthe fibrous web or a binder fiber as defined below. The thermoset binderis preferably selected from phenolic resin, acrylic concentration of thethermoset binder is selected such that effectively most of the fibers ofthe fibrous mixture are coated with the thermoset binder.

In an embodiment, the fibrous media comprises a coating made ofthermoset binder, selected from the group of phenolic resins, acrylicresins, epoxy resins, melamine formaldehyde resins and combinationsthereof.

Preferably the thermoset binder has a concentration of from 15% to 30%of the fibrous web by weight.

To further improve internal bonding between the fibers of the media, forexample between the first and second fibers, bicomponent thermoplasticfibers (as specific binder fibers) can be employed. Such fiberstypically comprise a thermoplastic core fiber surrounded by a meltablesurface layer of a thermoplastic polymer which as a lower melting pointthan the material forming the core. The low melting point thermoplasticpolymer may act as a thermoplastic binding agent when softened orpartially melted during processing of the fibrous web by heating,thereby adhering to the fibers of the web. The higher melting materialforming the core may act as a structural material. The average fiberdiameter of these bicomponent thermoplastic fibers may be preferably inthe range of about 2 to 20 um such as 10 um and the average fiber lengthof these bicomponent thermoplastic fibers may be preferably in the rangeof about 2 to 12 mm, such as about 6 mm. The amount of such fibers is0.1 to 20% by weight, preferably about 0.5 to 5% by weight, based on thetotal weight of fibers.

Moreover, to further improve internal bonding between the fibers of theweb, for example between the first and second fibers, other binderfibers can be employed. Such binder fibers are preferably thermoplasticbinder fibers such as PET binder fibers or polyvinyl alcohol (PVOH)binder fibers. These binder fibers have typically a lower melting pointthan the synthetic fibers, thereby acting as a binding agent whensoftened or partially surface-melted during processing of the fibrousweb by heating. Alternatively, these binder fibers do not melt, butbegin to partially dissolve in the solvent used for the manufacturingprocess (i.e. water) and become tacky. The tacky or softened binderfibers are therefore capable of internally binding the fibers of the webby adhering to the fibers and structurally strengthening the thusobtained fiber web. The average fiber diameter of these binder fiberslength of these binder fibers may preferably be in the range of about 2to 12 mm, such as about 6 mm. The amount of such fibers may be 0.1 to25% by weight, preferably about 0.5 to 20% by weight, such as 2% byweight, based on the total weight of fibers.

The present web optionally includes at least one additive which iscommon in the art. The at least one additive may be selected from aflame-retardant agent, a coloring agent, a hydrophobic agent, ahydrophilic agent, a wetting agent, an antimicrobial agent or anantistatic agent.

In an embodiment, the fibrous media may further comprise a nanofibercoating made of nanofibers, in particular electrospun nanofibers such asthose selected from polyethersulfone (PES) or polyamide (PA) nanofibers.The nanofiber coating may preferably have a thickness of about 50 to1000 nm. The nanofiber coating may preferably have a loading of about0.5 to 5.0 g/m². The nanofibers may preferably have an average fiberdiameter of about 50 to 500 nm such as about 100 to 300 nm. Preferably,the nanofiber coating may be applied on top of the fibrous web beingimpregnated with the thermoset binder.

The fibrous media is prepared generally by mixing fibers of at least onefirst fibrous component, optionally with at least one binder fiberand/or at least one additive, to form a fibrous web. The process isdisclosed in more detail in example 1.

According to a preferred embodiment the fibrous web of the presentdisclosure further has the following properties:

-   -   the basic weight between 50 and 400 gsm;    -   an air permeability for oil application of between 2 and 600        cfm/sf; and    -   a burst strength after 500 hours in hot oil having e.g. a        temperature of 140° C. of at least 20 psi.

Unless otherwise indicated, all parameters of the fibrous web describedherein were determined according to the tests methods described below inthe examples.

to 60 mils:

-   -   burst strength, dry (saturated and dried web, SD) typically 25        to 90 psi, in particular 28.5 to 85.0 psi;    -   burst strength, wet (saturated and dried web, SD) typically 10        to 90 psi, in particular 12 to 82.0 psi;    -   500 hour hot oil burst 20 to 50 psi.

Furthermore, typical properties of the fibrous media are the followingat a caliper (TMI) of 20 to 60 mils:

-   -   burst strength, dry (saturated, dried and cured web, SDC)        typically 30 to 80 psi;    -   burst strength, wet (saturated, dried and cured web, SDC)        typically 30 to 90 psi.

In an embodiment, stiffness (machine direction, MD, saturated and dried,SD) of a filter media having a caliper of 20 to 60 mils is typically3,300 to 10,000 mg, in particular about 5,000 to 8,000 mg.

In an embodiment, stiffness (machine direction, MD, saturated, dried andcured, SDC) of a filter media having a caliper of 20 to 60 mils istypically 3,200 to 16,800 mg.

In an embodiment, filtering efficiency of a web having a caliper of 20to 60 mils against particles having a particle size of 15 microns is: 20to 99%, in particular about 25 to 98%. Dirt holding capacity: 70 to 150mg/in², in particular 95 to 145 mg/in².

“Saturated and dried” stands for a medium having a total content ofvolatiles of less than 7% by weight at room temperature, based on thetotal weight of the medium.

“Saturated, dried and cured” stands for a medium having a total contentof volatiles of less than 7% by weight at room temperature, based on thetotal weight of the medium which has been fully cured.

A method of making a filter media of any of the above-discussedembodiments comprises typically the steps of

-   -   optionally at least one additive and/or at least one binder        fiber in water;    -   drying the web to a low moisture content, preferably a moisture        content of 2% or less;    -   contacting the dried web with a composition of a thermoset        binding agent in a liquid phase to bond the fibers together with        the thermoset binder;    -   removing the liquid phase to form a web;    -   optionally pre-curing and/or corrugating the web; and    -   pleating the web, optionally followed by a final curing step.

The concentration (solid matter) of the binding agent in the liquidphase composition is suitably about 10 to 50% by weight, based on thetotal weight of the liquid phase composition.

In the step of contacting the dried web with a binding agent, the driedweb is preferably saturated with a liquid composition of the thermosetbinding agent on one or both sides. After the saturation step, theliquid phase, i.e. the solvent or dispersing agent, of the compositionis removed. For removing the liquid phase the medium is preferablyheated.

Optionally, the dried medium may be pre-cured by an additional heatingstep prior to pleating and/or corrugation. “Pre-curing” refers to apartial curing of the thermoset binder resin up to e.g. 65% or 100%.

The liquid phase of the binding agent composition is, in one embodiment,removed such that the volatiles content is reduced to less than 10wt.-%, in particular less than 8 wt.-%, calculated from the total weightof the treated web prior to optional corrugation.

The content of volatiles refers to the amount of volatile componentsleft in the web at ambient (room) temperature.

The media can be optionally corrugated. In one embodiment, thecorrugation may be formed after impregnation of the fibrous web with athermoset binder by heating (or drying) the fibrous web to approximately180-220° C. between resin coating rolls and corrugation rolls, order toprevent the collapse of the corrugation by high heating. Corrugationtechniques are commonly known in the art.

The manufacturing method is examined in more detail in connection withExample 1.

The media can be pleated and optionally fully cured as described in moredetail in Example 3.

A fibrous media according to the present technology is capable offorming a self-supporting oil filter media which retains its pleats andcorrugations during periods of normal operation.

Typically, the present media is capable of retaining the pleats andoptionally corrugations even upon a contact with oil, in particular oilhaving a temperature of up to about 140° C. Thus, the self-supporting,pleated and optionally corrugated oil filter media is capable ofretaining pleats and optional corrugations upon contact with oil havinga temperature in the range encountered in a combustion engine such as125 to 135° C.

As preliminarily discussed above, it is known that e.g. heavy dutydiesel engines may have internal cracks in the gaskets within theircooling system which gives rise to a leaking of the ethylene glycol ofthe coolant into the lube oil of the lubrication system. The combinationof glycol with hot oil may have a dramatic influence on synthetic filtermedia, i.e. these media may lose their integrity and may even dissolvecompletely in the oil glycol mixture at elevated engine operatingtemperature.

By contrast, in the present invention it was observed that thesolubility of the fiber media according to the invention in glycol oilmixture is reduced or completely eliminated when the fibers areimpregnated or coated with a binder selected from the group of thermosetbinder resins like melamine-based resins, such as melamine formaldehyde.

According to an embodiment, the present disclosure concerns an oilfilter comprising a self-supporting pleated and optionally corrugatedfibrous media according to the present disclosure. The filter accordingto the present disclosure is especially suitable for use in lube oilsystems because of its high temperature integrity. A “filter” refers toa filter device (or corrugated and being disposed between a pair of endplates in such a manner so as to form a hollow cylinder. However, thefilter according to the present disclosure can be used also e.g. for gasturbine and clean room applications.

According to another embodiment, the web of the present disclosure maybe used in a laminated media product. Since the fibrous media accordingto the present disclosure contains a very high percentage of syntheticfibers, it is bondable to other materials in a lamination process usingheat bonding, ultrasonic bonding, etc. It may also be laminated usingstandard water-based or hot-melt glues.

The examples below discuss the production of filter media according tothe invention.

FIG. 2 shows the natural logarithm (ln) of the hot oil burst strength of(i) an exemplary web of the present disclosure and (ii) standard oilmedia as a function of time. The slope of the natural logarithm (ln)burst graph shown in FIG. 2 is considered to be the degradation rate ofthe media. The slope of the media according to the present disclosure ishalf of that of wood pulp-containing prior art media. Accordingly, themedia according to the present disclosure has higher burst strength fora significantly longer period of time on exposure to hot engine oil whencompared to a wood pulp-containing media.

It was observed that the groove depth (or corrugation depth) of themedia according to the present disclosure is stable in hot engine oiland is directly comparable to the groove depth retention in a typicalwood pulp-containing media. It is also observed that the relativelyheavy basis weight of the fibrous media according to the presentdisclosure, coupled with the relatively high % resin content of thesheet (e.g. at least 15% or 25% resin content) and the use of a phenolicresin system all combined to give the media excellent grooving andpleating characteristics as well as high durability in hot oil.

EXAMPLES Test Methods

Basis Weight: The basis weight is measured according to TAPPI Standard T410 om-02 and reported in grams per square meter (gsm).

TAPPI Standard T 411 om-05 using a Thwing Albert 89-100 ThicknessTester.

Corrugation Depth is the difference between the caliper of the flatsheet of media and the thickness of the sheet after corrugating themedia.

Air Permeability: The air permeability, or “air perm”, of the media ismeasured according to TAPPI Standard T 251 cm-85 (“Air Permeability ofPorous Paper, Fabric and Pulp Handsheets) with 0.5 inch (2.7 mm) waterdifferential using a Textest AG (model FX3300) and reported as the rateof the flow of air in cubic feet per square foot of sample area perminute (cfm/sf), sometimes referred to as cfm. Air Perm may also bereferred to porosity, Frazier or Textest.

Burst Strength: The wet and dry burst strength is measured according toTAPPI Standard T 403 om-22 (“Bursting Strength of Paper”) and reportedin kg_(f)/cm².

Stiffness of the media was determined according to TAPPI T 489 om-92using a Gurley bending resistance tester MOD 4171D (Gurley PrecisionInstruments).

Pore Size: The size of the pores in the media was determined using abubble point method according to ASTM 316-03 (2011) utilizing aPorometer G3 Series (Quantachrome Instruments) and reported in microns(μm).

Void fraction was determined by an imbibition method by immersing thefilter to be analyzed, under vacuum, in n-butyl alcohol that wets thepores (filter size: 40 mm×40 mm; vacuum pump: 0.133 Pa (ultimatepressure), 50 L/min exhaust rate; use a direct-reading balance having aresolution of at least 0.1 mg).

Dust Holding Capacity/Particle Removal Efficiency: Following ISO 4548-12for lube oil filtration using a Multipass system, the DHC (Dust HoldingCapacity) and particle removal efficiency was determined for the media.The media is tested as a flat sheet with a test flow of 0.5 L/min,particle injection flow of 250 mL/min, BUGL (Basic Upstream Gravimetric

shaped sample test diameter of 6.375 inches, and a face velocity of3.624 inches per minute.

Hot Oil Ageing, in order to determine the hot oil burst strength, isdone by placing a media sample (size: 14×10 cm) into an oil bath oftypical engine oil (e.g. Mobil 1) maintained at 140 C+/−0.1° C. for 500hr. “Hot oil burst strength” of a media sample is defined as the maximumhydrostatic pressure required to result in rupture of the media samplewhen a controlled and constantly increasing pressure is applied througha rubber diaphragm to an area of 7.07 cm². The media sample is thenremoved, cooled for about 5 minutes, and excess oil is blotted from thesample. Then, the moisture free sample is tested using a Mullen burststrength tester. The results are reported in force per unit area atfailure (e.g. kg/cm² or psi).

Unless otherwise indicated, the unit “um” corresponds to “μm” or micron.

Manufacture of Filter Material (Example 1)

The production process for making a filtration media comprises forexample a wet-laid process. In such a process, the fibrous material isfirst disintegrated for example in a hydropulper optionally in thepresence of a fiber dispersant chemical additive such as a surfactantfor keeping the fibers separated when added and to prevent the fibersfrom entangling during handling. If microglass is being disintegrated,the pH of the hydropulper may also be adjusted to a pH in the range of 2to 5 using an acid in order to prevent the microglass fibers fromclumping together and to promote even dispersion of the microglassfibers. Fibers of each desired variety are then added to the hydropulperin their respective correct proportion according to the furnish recipe.A consistency (fiber weight to water volume) of about 1 to 10%, inparticular about 5% is preferred at the mixing stage.

After an optional refining stage, the fiber furnish is then diluted downto a consistency of about 0.01-0.02% and formed into a web on a papermachine wire. A single layer or multiple layer headbox design may beemployed. If a multiple layer headbox design in employed, more than onedesigned furnish blend may be deposited in series onto the paper machinewire, thereby creating a multi-layer wet-laid composite.

the moving paper machine wire by a series of hydrofoils and vacuum boxesuntil the percent solids content of the sheet is approximately 30 to 40wt-%. In a subsequent dryer section, the web is dried to approximately amoisture content of 2% or less.

The binder resin is then introduced to the sheet, preferably at asaturator machine. The resin may be applied on either one or both sidesof the sheet. The process may be adjusted to achieve either 1- or2-sided saturation of the sheet. The solids content of the resin bathapplied to the sheet is typically between 20 to 40 wt-%. The resin bathsolids content is chosen based on multiple processing (equipment) andapplication (into the web) considerations. Besides the solids content,the balance of the resin bath composition is a solvent such as methanol,water, and/or other solvent components.

After the resin is applied to the sheet, the solvent is liberated byheating the web to an elevated temperature such that the solventevaporates at a rate fast enough to accommodate the desired productionthroughput. Heating may involve the use of steam cans, ovens, acombination of both, and/or other heating technologies. The obtainedmedia may be referred to as being “saturated and dried (SD)”.

After the solvent removal, the media may be pre-cured by heating to anelevated temperature such that the binder resin partially (e.g. to25-65%) and/or completely cures. Heating may involve the use of steamcans, ovens, a combination of both, and/or other heating technologies.The thus obtained media being completely cured may be referred to asbeing “saturated, dried and cured (SDC)”.

During this drying process groove patterns (corrugation), if applicable,can be also imparted on the sheet. This may be most preferably done bycalendering the resulting wet-laid fibrous sheet under heat (up to 220°C.) and pressure using both top and bottom hot smooth rolls, therebypreferably adjusting the obtained sheet's void fraction in the range ofapproximately 70-95%, such as 80-90% which is beneficial forcorrugation. The percent volatiles content is reduced in the dryingprocess to a predetermined level of about 1 to 10%, in particular toabout 4 to 6%, by weight of the web.

shown in Table 1.

TABLE 1 Summary of furnish compositions Samples 1 and 2 Fiber Sample 1Sample 2 4 mm “PVOH fiber”,  2.0% by weight — average fiber diameter: 10μm (binder fiber) glass fibers, average  4.0% by weight 10.0% by weightfiber diameter: 0.65 μm glass fibers, average 16.5% by weight 10.0% byweight fiber diameter: 2.44 μm PET 0.3 D*5 mm, 16.4% by weight 30.3% byweight average fiber diameter: 5.5 μm PET 0.8 D*5 mm — 11.0% by weightPET 0.8 D*6 mm,  6.6% by weight — average fiber diameter: 9.06 μmLyocell 1.7 Dt*4 mm, 34.5% by weight — unfibrillated, average fiberdiameter: 11.5 μm Undrawn PET 20.0% by weight 38.7% by weight 1.6 D*5 mmResin content   25% by weight   25% by weight phenolic melamine (phenolformaldehyde resin) Cellulosic content 34.5% by weight — Glass content20.5% by weight 20.0% by weight Total content of 45.0% by weight 80.0%by weight thermoplastic fibers

Properties of the exemplary webs according to the present disclosure areshown in Table 2.

TABLE 2 Properties of exemplary webs (Samples 1 and 2) Unit Sample 1Sample 2 Basis weight (SD) lb/3000 ft² 162.0 114.7 g/m² 263.6 186.6Basis weight (SDC) lb/3000 ft² 150.8 109.3 g/m² 245.4 177.8 Textest airpermeability cfm 39.8 28.8 TMI Caliper (or thickness) mils 52.3 36.2 mm1.33 0.92 Groove (or corrugation) depth mils 18.0 5.0 (see FIG. 5) mm0.46 0.13 Mean pore (manual) μm 18.2 15.6 Burst—dry, SD psi 28.5 80.0Burst—wet, SD psi 18.5 65.0 Burst—wet, SDC psi 48.0 67.0 Stifthess, MDSD mg 4 900 7 900 Stifthess, MD SDC mg 9 100 6 800 Particle removalefficiency % 81.9 96.2 against particles having a particle size of 15microns Dirt holding capacity (DHC) mg/in² 144.1 100.9 mg/cm² 22.3 15.6500 hour hot oil burst (Hot psi 23.3 43.0 Oil Ageing) kPa 160.9 297kgf/cm² 1.64 3.02

Example 2 (Samples 3-6)

Using the method described in Example 1, filter media impregnated withmelamine resin were produced (Samples 3-6). For Samples 5 and 6, anadditional calendaring step for adjusting the void fraction to a rangeof about 70-95%, as discussed above, was used for preparing thecorrugated filter media. Corrugation on the sheet was imparted duringthe drying process at a temperature of about 180-220° C., followed by atemperature below 80° C. after the corrugation was completed. Thecompositions of Samples 3-6 are given in Table 2a below.

The properties of the filter media thus obtained are indicated in Tables3 and 4. The medium of Sample 3 is suitable for, e.g., motorcycle fuelmedia filters. The medium of Sample 4 is self-supporting, washable andplain e.g. flat. It is suitable for, e.g., lube (oil) and airapplications. The medium of Sample 5 is self-supporting, washable andcorrugated and suitable for, e.g., lube (oil) and air applications.

TABLE 2a Summary of furnish compositions Samples 3, 4, 5 and 6 FiberSample 3 Sample 4 Sample 5 Sample 6 Glass fibers, average fiber  8.0% by10.0% by 10.0% by — diameter: 0.65 μm weight weight weight Glass fibers;average fiber — — —  8.0% by diameter: 0.53 μm; weight Glass fibers,average fiber — 10.0% by 10.0% by 13.3% by diameter: 2.44 μm weightweight weight PET 0.05 D*6 mm  8.9% by — — — weight PET 0.3 D*5 mm,average 17.8% by 30.3% by 30.3% by 43.7% by fiber diameter: 5.5 μmweight weight weight weight PET 0.8 D*5 mm 17.8% by 11.0% by 11.0% by —weight weight weight PET 1.4 D*6 mm  8.9% by — — — weight PET 3.0 D*5 mm 8.9% by — — — weight Undrawn PET 29.7% by 38.7% by 38.7% by 35.0% by1.6 D*5 mm weight weight weight weight Resin content (=amount 18.5% by21.9% by   17% by   23% by of resin based on the total weight weightweight weight weight of the fibrous melamine melamine melamine melaminemedia) Glass content  8.0% by 20.0% by 20.0% by 20.0% by weight weightweight weight Total content of 92.0% by 80.0% by 80.0% by 80.0% bythermoplastic fibers weight weight weight weight

Physical Sample Sample Sample properties 3 4 5 Mass per g/m² SD 216.8199.8 187.2 unit area SDC 208.3 193.2 181.7 (basis weight) Thickness 20kPa mm Total — — 1.008 Caliper 1.334 1.098 0.893 Corrugation mm — —0.115 depth Air 125 Pa cfm/sq. ft 32.1 30.8 28.5 permeability Burstkgf/cm² SD 3.19 4.87 4.22 Strength, dry psi 45.4 69.3 60.0 Pore Size μmMax 63.9 44.0 47.4 Mean 54.6 39.7 41.8 Stiffness mg SD 5957 9778 4801Dirt holding mg/in² 74.1 73.7 90.8 capacity (mg/cm²) (11.48) (11.42)(14.07)

The properties of the filter medium of Sample 6 are indicated in Table4. The medium is self-supporting, pleatable and corrugated.

TABLE 4 Properties of exemplary Filter Medium (Sample 6). Overallfiltration efficiency (ISO 4548-12) against particles having thefollowing particle size: >10 μm  96.6% >12 μm  99.1% >15 μm  99.9% >17μm 100.0% >20 μm 100.0% >25 μm 100.0% >30 μm  99.9% >40 μm  99.9%Corrugation depth 0.15-0.6 mm

Example 2a

Using the method described in Example 1, a filter medium comprising abinder fiber and being impregnated with melamine resin (Sample 7) or afilter medium comprising a binder fiber (Samples 8 to 9) was produced.The compositions of Samples 7-9 and Comparative Samples 1-3 are given inTables 5 and 6 below.

TABLE 5 Summary of furnish compositions Sample 7 and Comparative Samples1-3 (see also FIG. 2) Compar- Compar- Compar- ative ative ative FiberSample 7 Sample 1 Sample 2 Sample 3 Softwood fibers — 57.0% by 70.7% by31.7% by weight weight weight Hardwood fibers — 13.3% by  3.0% by 50.7%by weight weight weight Glass fibers, average fiber 15.5% by —  2.3% by— diameter: 2.44 μm weight weight Glass fiber, average fiber — —  6.0%by  3.3% by diameter: 0.65 μm weight weight PET 0.3 D*5 mm, average33.2% by — — — fiber diameter: 5.5 μm weight PET 0.8 D*6 mm 10.3% by — —— weight Reliance 1.5 d × ¼″ — 30.0% by 18.0% by 14.3% by polyesterweight weight weight Lyocell 1.7 Dt*4 mm, 31.5% by — — — unfibrillated,average fiber weight diameter: 11.5 μm Binder PET 2.0 D*6 mm  9.5% by —— — (binder fiber) weight Resin content (=amount of   25% by 26.0% by22.0% by 18.0% by resin based on the total weight weight weight weightweight of the fibrous phenolic phenolic phenolic phenolic media)Cellulosic pulp content — 60.0% by 73.7% by 82.4% by weight weightweight Glass content 15.5% by —  8.3% by  3.3% by weight weight weightTotal content of 84.5% by 30.0% by 18.0% by 14.3% by thermoplasticfibers weight weight weight weight

The hot oil burst strength properties of the filter media thus obtained(Sample 7 and Comparative Samples 1-3) are shown in FIG. 2.

TABLE 6 Summary of furnish compositions Samples 8-9. Fiber Sample 8Sample 9 PET 0.06 Dt*3 mm  14.8% by  14.8% by weight weight PET 0.3 D*5mm, average  65.6% by  65.6% by fiber diameter: 5.5 μm weight weightBinder 4.0 D*6 mm  19.7% by  19.7% by (bicomponent binder fiber) weightweight Nanofiber coating PES PA (thermoplastic, (thermoplastic, 50-1000nm) 50-1000 nm) Resin content acrylic resin, acrylic resin,    7% by   7% by weight weight Glass content — — Total content of 100.0% by100.0% by thermoplastic fibers weight weight

Example 3: Pleating of Material

The material can be pleated to provide a suitable self-supporting,pleated, stand-alone structure.

In the pleating process the media is loaded between two rollers. The nipgap between the roller and the scoring head between the nip gap helps toform the fold mark for the pleat. The pleat is formed by the forwardmovement of the media post fold mark. The fold is then made to movethrough a preheating zone at 150 to 160° C. with a very short residencetime 15-120 sec.

The folded media can then be allowed to pass through an oven to completeresidual cure at 180° C. or higher for a residence time of 5-10 min. Thecuring oven is optional and used only if the media is uncured orpartially cured at the previous stage.

The pleatability of a material can be assessed by the pleat angle whichwill reflect the extent or ease of forming a pleat.

On the other hand, an important feature of the present invention is thecombination of ease of pleat forming during manufacturing of the fibrousmedia and pleat-retention upon contact with hot oil.

An exemplary pleated self-supporting web according to present disclosureprocessed as described above is shown in FIG. 3, wherein referencenumeral 11 refers to the pleated material.

The specific examples provided in the description given above and thespecific embodiments provided below should not be construed as limitingthe scope and/or the applicability of the appended claims.

Specific Embodiments

Further specific embodiments and suitable feature combinations thereofare described below:

-   1. A fibrous media suitable for an oil filter comprising a fibrous    web formed from, or comprising, (i) synthetic fibers; (ii)    optionally at least one additive; (iii) a thermoset binder present    at a concentration of at least 15 wt-% by weight of the fibrous web    and/or (iv) at least one binder fiber. Most preferably, the fibrous    web does not include regenerated cellulosic fibers such as Lyocell    or viscose or combinations thereof. The at least one binder fiber    preferably comprises an amount of 2 to 25 wt.-%, based on the total    weight of the fibers. The synthetic fibers comprise up to 40 wt.-%,    preferably up to 30 or up to 20 wt.-%, glass fibers, based on the    total weight of the fibers. Preferably, the synthetic fibers    comprise up to 70 wt.-%, preferably up to 80 wt.-%, thermoplastic    fibers, based on the total weight of the fibers. Preferably, said    thermoplastic fibers comprise undrawn thermoplastic fibers,    preferably in an amount of 15 to 50 wt.-%, such as 20 to 40 wt.-% by    weight, based on the total weight of the fibers. The synthetic    fibers are internally bonded with the thermoset binder and/or the    binder fiber to form the fibrous web. The thus obtained fibrous    media may be capable of forming a self-supporting, optionally    corrugated and pleated oil filter which is preferably capable of    retaining pleats and optional corrugations upon contact with oil    having a temperature in the range encountered in a combustion    engine. Preferably, this fibrous media does not contain natural wood    pulp.-   2. The fibrous media according to embodiment 1, comprising synthetic    fibers selected from the group of thermoplastic polymers, silicious    fibers, such as glass fibers, regenerated cellulosic fibers and    mixtures thereof, at least 30 wt-%, preferably at least 50 wt-%,    more preferably at least 80 wt.-%, of the fibers being thermoplastic    polymers.-   3. The fibrous media according to embodiment 1 or 2, wherein the    fibrous web contains (i) at least 70 wt-% fibers such as at least 80    wt-% of thermoplastic polymer(s) and up to 40 wt-% such as up to 30    wt-% regenerated cellulosic fibers. An alternative embodiment is the    fibrous media according to embodiment 1 or 2, wherein the fibrous    media contains (ii) at least 70 wt-% fibers of thermoplastic    polymer(s). Another alternative embodiment is the fibrous media    according to embodiment 1 or 2, wherein the fibrous media contains    no regenerated cellulosic fibers such Lyocell or viscose or    combinations thereof-   4. The fibrous media according to any of the preceding embodiments,    comprising a fibrous web impregnated with the thermoset binder.-   5. The fibrous media according to any of the preceding embodiments,    wherein the binder fiber is selected from a bicomponent binder    fiber, a polyethylene terephthalate (PET) binder fiber or a    polyvinyl alcohol (PVOH) binder fiber. Preferably, the amount of    these binder fibers is 0.1 to 25 wt.-% such as 1 to 20 wt.-% or 2 to    10 wt.-%, based on the total weight of fibers.-   6. The fibrous media according to any of the preceding embodiments,    wherein the at least one additive is selected from a flame-retardant    agent, a coloring agent, a hydrophobic agent, a hydrophilic agent, a    wetting agent, an antimicrobial agent or an antistatic agent.-   7. The fibrous media according to any of the preceding embodiments,    comprising 15 to 30 wt.-%, in particular 20 to 25 wt.-%, of the    thermoset binder, based on the total weight of the synthetic fibers.-   8. The fibrous media according to any of the preceding embodiments,    wherein the thermoset binder is selected from thermoset resins, such    as phenolic resins, epoxy resins or melamine-based polymers, such as    melamine formaldehyde, or acrylic resins, or combinations thereof-   9. The fibrous media according to any of the preceding embodiments,    comprising synthetic fibers comprising first fibers, having a first    average diameter such as e.g. less than 1 um, and second fibers,    having a second average diameter such as e.g. 2 um or more, the    first average diameter being less than the second average diameter.    Preferably, said synthetic fibers are glass fibers. The weight ratio    of the two groups of fibers may be 1:100 to 100:1, in particular    about 1:10 to 10:1.-   10. The fibrous media according to any of the preceding embodiments,    wherein the synthetic fibers comprise undrawn fibers such as undrawn    thermoplastic polyethylene terephthalate fibers, preferably in an    amount of 15 to 50% by weight, more preferably 30 to 40% by weight,    based on the total weight of fibers.-   11. The fibrous media according to any of the preceding embodiments,    wherein the thermoplastic fibers are selected from the group of    polyesters, for example polyalkylene terephthalates, such as    polyethylene terephthalate (PET), polybutylene terephthalate (PBT)    and the like, polyalkylenes, for examples polyethylenes,    polypropylenes and the like, polyacrylonitriles (PAN), and    polyamides, for example nylons, such as nylon-6, nylon 6,6,    nylon-6,12, and the like, and combinations thereof, in particular a    majority of the synthetic fibers comprises polyester fibers such as    preferably more than 70% or even more than 75% of the synthetic    fibers.-   12. The fibrous media according to any of the preceding embodiments,    wherein the synthetic fibers comprise thermoplastic synthetic fibers    having an average fiber diameter from 0.1 um to 15 um, such as 1 to    10 um and an average fiber length from 1 to 20 mm, such as 1 to 10    mm or 1 to 7 mm.-   13. The fibrous media according to any of the preceding embodiments,    wherein the glass fibers have an average fiber diameter of 0.4 to    2.6 um.-   14. The fibrous media according to any of the preceding embodiments,    wherein the synthetic fibers include up to 40% by weight or up to    30% by weight or up to 20% by weight or even only up to 10% by    weight, based on the total weight of the fibers, of a regenerated    cellulosic material, such as Lyocell or viscose or combinations    thereof.-   15. The fibrous media according to any of the preceding embodiments,    wherein the fibers consist essentially of fibers of a synthetic    material having a glass transition point or melting point greater    than 130° C., in particular greater than 150° C.-   16. The fibrous media according to any of the preceding embodiments,    wherein the fibrous media has an average thickness of 0.6 to 1.5 mm,    in particular 0.7 to 1.4 mm.-   17. The fibrous media according to any of the preceding embodiments,    wherein the fibrous web is corrugated, preferably by a corrugation    depth of about 0.1 to 0.5 mm.-   18. The fibrous media according to any of the preceding embodiments,    wherein the fibrous media further comprises a nanofiber coating,    wherein the nanofiber coating includes nanofibers, such as    polyethersulfone (PES) or polyamide (PA) nanofibers. Preferably, the    nanofiber coating's thickness is 50 to 1000 nm. Preferably, the    nanofibers have an average fiber diameter of 50 to 500 nm such as    100 to 300 nm. Preferably, the nanofibers are applied using    electrospinning Preferably, the nanofiber coating is applied on top    of the fibrous web being impregnated with the thermoset binder.-   19. The fibrous media according to any of the preceding embodiments,    wherein the fibrous web is wet-laid.-   20. The fibrous media according to any of the preceding embodiments,    wherein    -   the basic weight of the fibrous web is between 50 and 400 gsm        such as 100 to 250 gsm;    -   the (air) permeability of the fibrous web for oil is between 2        and 600 cfm/sf; and    -   the hot oil burst strength of the fibrous web after 500 hours in        140 C hot oil is at least 20 psi or at least 30 psi.-   21. The fibrous media according to any of the preceding embodiments,    wherein    -   the fibers of the thermoplastic polymer form 60% to 88% of the        fibrous web by weight;    -   the glass fibers form 2% to 30% of the fibrous web by weight;        and    -   the fibrous web further comprises a coating made of the        thermoset binder composed of a phenolic resin, an acrylic resin,        an epoxy resin or a melamine formaldehyde, wherein the amount of        the binder is from 15% to 30 wt.-% by weight of the fibrous web.-   22. The fibrous media according to any of the preceding embodiments,    wherein said fibrous media exhibits at a caliper of 20 to 60 mils at    least one, preferably a combination of two, in particular all three,    of the following parameters:    -   a stiffness (SD), in machine direction, of 3,300 to 10,000 mg,        in particular about 5,000 to 8,000 mg;    -   a filtering efficiency against 15 micron particles of: 20 to        99%, in particular about 25 to 98%; and    -   a dirt holding capacity of 70 to 150 mg/in², in particular 95 to        145 mg/in².-   23. The fibrous media according to any of the preceding embodiments,    wherein the fibers consist of synthetic fibers only.-   23. A method of making a filtration media or the fibrous media of    embodiments 1 to 22, comprising    -   forming a wet laid web from a fibrous slurry comprising        synthetic fibers, optionally at least one binder fiber and        optionally at least one additive, in water;    -   drying the web to a moisture content of 2% or less;    -   contacting the dried web with a composition of a thermoset        binding agent in a liquid phase to bond the fibers together with        the thermoset binder; and    -   removing the liquid phase to form the fibrous media;        the fibrous media thus obtained being capable of forming a        self-supporting, pleated oil filter media which is capable of        retaining pleats upon contact with oil having a temperature in        the range encountered in a combustion engine.-   24. The method according to embodiment 23, wherein the dried web is    saturated with a liquid composition of the thermoset binding agent    on one or both sides, and subsequently the liquid phase of the    composition is removed in particular by heating the web.-   25. The method according to embodiment 24, wherein, during the    removal of the liquid phase of the composition in particular by    heating the web the web is pre-cured and/or a corrugation pattern is    applied on the web.-   26. The method according to any of embodiments 23 to 25, wherein the    fibrous media is pleated, and optionally fully cured, thereby    forming the self-supporting, pleated oil filter.-   27. The method according to embodiments 23 to 26, wherein the liquid    phase of the binding agent composition is removed such that the    volatiles content is reduced to less than 10 wt-%, in particular    less than 8 wt-%, calculated from the total weight of the treated    web.-   28. The method according to any of embodiments 23 to 27, wherein the    media comprises at least 15 wt.-%, preferably 15 to 30 wt.-%, in    particular 20 to 25 wt.-%, of a thermoset binder, based on the total    weight of the fibers.-   29. The method according to any of embodiments 23 to 28, wherein the    thermoset binder is selected from thermoset resins, such as phenolic    resins, epoxy resins or melamine-based polymers, such as melamine    formaldehyde, or acrylic resins, and combinations thereof-   30. The method according to any of embodiments 23 to 29, wherein the    thermoplastic fibers are selected from the group of polyesters, for    example polyalkylene terephthalates, such as polyethylene    terephthalate (PET), polybutylene terephthalate (PBT) and the like,    polyalkylenes, for examples polyethylenes, polypropylenes and the    like, polyacrylonitriles (PAN), and polyamides, for example nylons,    such as nylon-6, nylon 6,6, nylon-6,12, and the like, and    combinations thereof-   31. The method according to any of embodiments 23 to 30, wherein    said media exhibits at a caliper of 20 to 60 mils at least one,    preferably a combination of two, in particular all three, of the    following parameters:    -   a stiffness (SD), in machine direction, of 3,300 to 10,000 mg,        in particular about 5,000 to 8,000 mg;    -   a filtering efficiency for 15 micron particles of: 20 to 99%, in        particular about 25 to 98%; and    -   a dirt holding capacity of 70 to 150 mg/in², in particular 95 to        145 mg/in².-   32. A filtration media or a fibrous media obtainable by the method    according to any one of embodiments 23 to 31.-   33. An oil filter comprising (i) the fibrous media according to any    of embodiments 1-22 or (ii) the filtration media or the fibrous    media according to embodiment 32.-   34. The oil filter according to embodiment 33, wherein the oil    filter media is pleated and optionally corrugated.-   35. Use of a thermoset resin for preventing damage of the oil filter    according to embodiments 32 to 34 caused by a combination of oil and    antifreeze agents and decomposition products thereof.

All possible combinations of embodiments, specific embodiments, aspectsand/or features of the invention as described above are also disclosedherewith.

1.-24. (canceled)
 25. An oil filter comprising a fibrous media, whereinthe fibrous media includes a fibrous web comprising: (i) syntheticfibers; and (ii) a binder component which is at least one selected fromthe group consisting of a thermoset binder present at a concentration ofat least 15 wt % by weight of the fibrous web and at least one binderfiber; wherein the synthetic fibers comprise up to 30 wt. % of glassfibers, based on the total weight of the fibers; and wherein thesynthetic fibers are bonded with the thermoset binder and/or the atleast one binder fiber to form the fibrous web; and wherein the fibrousmedia is capable of forming a self-supporting, pleated oil filter whichis capable of retaining pleats upon contact with oil having atemperature in the range encountered in a combustion engine; and thefibrous media is not reinforced with an additional mechanical supportlayer.
 26. The oil filter according to claim 25, wherein the syntheticfibers of the fibrous web comprise at least at least 30 wt.-% ofthermoplastic polymer fibers.
 27. The oil filter according to claim 25,wherein the synthetic fibers of the fibrous web comprise fibers selectedfrom the group consisting of silicious fibers, regenerated cellulosicfibers and mixtures thereof.
 28. The oil filter according to claim 25,wherein the fibrous web comprises: (i) at least 70 wt.-% fibers ofthermoplastic polymer(s) and up to 40 or up to 30 wt.-% regeneratedcellulosic fibers; (ii) at least 70 wt.-% fibers of thermoplasticpolymer(s); or (iii) no regenerated cellulosic fibers.
 29. The oilfilter according to claim 25, wherein the fibrous web is impregnatedwith the thermoset binder which is selected from the group consisting ofthermoset resins, epoxy resins, melamine-based polymers, acrylic resinsand combinations thereof.
 30. The oil filter according to claim 25,wherein the binder fiber is selected from the group consisting ofbicomponent binder fibers, polyethylene terephthalate (PET) binderfibers and polyvinyl alcohol (PVOH) binder fibers.
 31. The oil filteraccording to claim 25, which further comprises at least one additive isselected from the group consisting of flame-retardant agents, coloringagents, hydrophobic agents, hydrophilic agents, wetting agents,antimicrobial agents and antistatic agents.
 32. The oil filter accordingto claim 25, wherein the fibrous media comprises 15 to 30% of thethermoset binder, based on the total weight of the fibers.
 33. The oilfilter according to claim 25, wherein the synthetic fibers comprisefirst fibers having a first average length and a first average diameterof 2 μm or more, and second fibers having a second average length and asecond average diameter less than 1 μm, wherein the first average lengthof the first fibers is greater than the second average length of thesecond fibers.
 34. The oil filter according to claim 25, wherein thesynthetic fibers comprise undrawn fibers in an amount of 15 to 50% byweight, based on the total weight of fibers; and/or wherein thesynthetic fibers are thermoplastic fibers selected from the groupconsisting of polyesters, polyalkylenes, polyacrylonitriles (PAN),polyamides and combinations thereof.
 35. The oil filter according toclaim 25, wherein the synthetic fibers comprise thermoplastic syntheticfibers having an average diameter from 0.1 um to 15 um, and an averagelength from 1 to 50 mm.
 36. The oil filter according to claim 25,wherein the glass fibers have an average fiber diameter of 0.4 to 2.6um.
 37. The oil filter according to claim 25, wherein the syntheticfibers include up to 40% by weight, based on the total weight of thefibers, of a regenerated cellulosic material selected from the groupconsisting of Lyocell, viscose and combinations thereof.
 38. The oilfilter according to claim 25, wherein the fibrous web is corrugated witha corrugation depth of about 0.1 to about 0.5 mm and has an averagethickness of 0.6 to 1.5 mm.
 39. The oil filter according to claim 25,wherein the fibrous media further comprises a nanofiber coating with athickness of 50 to 1000 nm, wherein the nanofiber coating includeselectrospun nanofibers selected from the group consisting ofpolyethersulfone (PES) nanofibers and polyamide (PA) nanofibers.
 40. Theoil filter according to claim 25, wherein the fibrous web comprises,based on fibrous web weight: 60 wt. % to 88 wt. % of thermoplasticpolymer fibers; 2 wt. % to 30 wt. % of glass fibers form 2% to 30%; and15 wt. % to 30 wt. % of a coating formed of the thermoset binderselected from the group consisting of phenolic resins, acrylic resins,epoxy resins and melamine formaldehyde resins.
 41. A method of making aself-supporting pleated oil filter comprising: (a) providing a fibrousmedia which includes a fibrous web comprising: (i) synthetic fiberscomprising up to 30 wt. % of glass fibers, based on the total weight ofthe fibers; and (ii) a binder component which is at least one selectedfrom the group consisting of a thermoset binder present at aconcentration of at least 15 wt % by weight of the fibrous web and atleast one binder fiber; wherein the synthetic fibers are bonded with thethermoset binder and/or the at least one binder fiber to form thefibrous web; and (b) pleating the fibrous media in the absence of anadditional mechanical support layer to form a self-supporting pleatedoil filter that is capable of retaining pleats upon contact with oilhaving a temperature in range encountered in a combustion engine. 42.The method according to claim 41, wherein the wherein the fibrous webcomprises on one or both sides a dried residue of a liquid compositionof the thermoset binding agent.
 43. The method according to claim 42,wherein the fibrous web is pre-cured.
 44. The method according to claim43, which further comprises corrugating the fibrous web to a corrugationdepth of about 0.1 to about 0.5 mm.